1. Field of the Invention
This invention relates to a corrosion protection system and a method of protecting certain articles from corrosion by enclosing the articles in a suitable enclosure and flushing the interior space of the enclosure with a continuous flow of non-corrosive gas, thereby preventing ambient corrosive gasses (or other corrosive agents) from contacting the protected articles.
This invention relates to movable, semi-permanent or temporary roof supports and cylinders used in coal mining or other underground mining. Movable, semi-permanent or temporary roof support apparatuses generally employ a roof engaging support and a ground-engaging base with hydraulic roof support cylinders positioned between a roof engaging support and a ground-engaging base. Hydraulic roof support cylinders are used in coal mining operations where gases or other agents, which are corrosive to cylinder exterior surfaces, may be present.
2. Description of Related Art
Temporary roof supports including temporary roof support cylinders as described in U.S. Pat. Nos. 5,950,673 and 5,026,218 are manufactured and sold by Joy MM Delaware Inc. The Joy roof support structure depends upon a hydraulic roof support cylinder which is plated with bronze and which is wiped infrequently by hydraulic fluids during use. As manufactured by Joy Mining Machinery, the roof support cylinders are coated with bronze for corrosion protection purposes. The cylinders may also be coated with other substitutions for bronze and brass. However, bronze was found in testing to be the best with Hydrogen sulfide. However, this material is corroded by at least hydrogen sulfide and, therefore, the cylinders require protection from prolonged contact with hydrogen sulfide gasses. During use, a roof support may be put in place with cylinders in an extended position, or only partially collapsed, thereby leaving at least some of its surfaces exposed for an extended period of time. This is especially true of semi-permanent roof supports as used in mining operations known as “longwall”. When bronze or other copper containing surfaces are exposed to atmospheres which may include hydrogen sulfide with possible high humidity conditions, corrosion of the bronze or other plating becomes severe. When cylinders are severely corroded, the cylinder is no longer capable of operation because of leakage at hydraulic cylinder seals. Under certain mining conditions, as many as 35 percent of the cylinders used in a mine may require replacement within one year, resulting in possible replacement of 130 cylinders per year in one mining operation. The replacement or repair of each cylinder costs in the order of $40,000 for a cost of $5,000,000 per year.
In the art of mining where coal gob is present, nitrogen gas may also be supplied to the mine in order to decrease the danger of mine fires, or to provide rapid introduction of nitrogen in the case of emergency. “Gob” is collapsed roof strata, often containing coal that is left behind in a mine behind a longwall as it advances. Therefore, nitrogen, which is a known non-combustible and non-corrosive gas, is readily available in certain mining operations. Nitrogen is used to dilute methane and oxygen gases in a mine and is readily available as a gas which can be used to protect against corrosion. However, it is to be understood that any inert gas or gas which does not attack a hydraulic cylinder may be used such as clean air.
U.S. Pat. No. 6,551,552 to Lyublinski relates to corrosion protection and protecting an article from corrosion by placing an article in a gas impermeable enclosure. This prior art differs from Applicant's invention in that Applicant maintains open orifices and a small positive pressure within the gas enclosure which continually flushes the gas enclosure with the inserted non-corrosive gas (nitrogen). The '552 patent further fails to suggest or teach any possible utility for protection of bronze plated cylinders which are subject to corrosion by hydrogen sulfide gas in coal mines. '552 recognizes the corrosive nature of sulfides, and the susceptibility of copper, bronze and brass to certain corrosion under normal atmospheric conditions. As taught by '552 in column 3, the gas impermeable enclosure would have no tears, leaks or pinholes which would allow the higher internal pressure to equalize with the slightly lower external pressure. Applicant's invention, on the other hand, provides for continuous controlled flow and an orifice to the outside to control pressure on the inside.